As the rapid development of planar display technology, Active Matrix Organic Light Emitting Diodes (AMOLED) have become a future development trend of displays due to their excellent characteristics such as being more slim, self-luminating and high reaction rate. An active matrix organic light emitting diode may comprise an active switch, an insulating layer, a transparent electrode, a light emitting layer and a metal electrode formed in turn on a substrate, wherein the active switch is connected to the transparent electrode through a contact vias to control writing of image data. At present, in order to accommodate the large scale trend of AMOLEDs, active switches generally use low temperature polysilicon TFTs (LTPS-TFTs) as control elements for switching pixels. The quality of low temperature polysilicon films for manufacturing LTPS-TFTs has direct impact on electric performance of LTPS-TFTs. Therefore, the manufacturing technology of low temperature polysilicon film attracts increasing attention.
For conventional AMOLEDs, such as manufacturing a polysilicon film in back plate technology, excimer laser annealing (ELA), solid phase crystallization (SPC), metal-induced crystallization (MIC) methods are mainly used; while obtaining polysilicon film in the active layer of the transistors in back plate with excimer laser annealing is the only method that has been realized mass production.
In the conventional excimer laser annealing technology, as shown in FIGS. 1 and 2, the substrate 203 is directly placed on a base or platform 204 (typically with a stainless steel surface) for annealing, and a thin film layer 202 is formed on the substrate 203. After heating treatment the thin film layer 202 under high temperature and laser annealing with a laser beam 201, the fabrication of polysilicon film is completed. Therein, the thin film layer 202 includes a silicon nitride layer 101, a silicon dioxide layer 102 and an amorphous silicon layer 103 formed subsequently on the substrate 203, wherein the silicon nitride layer 101 and the silicon dioxide layer 102 form a buffer layer. In the manufacturing process of said low temperature polysilicon film, since the substrate 203 contacts the base 204 directly, heat transfer rate is fast, resulting in the short cooling time for the molten silicon layer (about 100 ns). The solidifying is too quick to allow the crystal nucleus to grow to larger size with enough time. Therefore, the manufactured polysilicon thin film transistor has a mobility significantly impacted by grain size.